The present invention relates to a voltage regulator circuit for providing voltage to an integrated circuit chip and to a method for regulating a voltage of an integrated circuit chip.
Voltage regulators, also called voltage downconverters, have become quite popular in todays integrated circuit chips, e.g. in memory, microprocessor and microcontroller areas. In particular, a chip with an on-chip voltage regulator can be operated with a single external power supply. Moreover, more than one level of internal power supply voltage can be generated for different applications in different operating modes. Using a lower power supply voltage reduces consumption by the circuit. Moreover, a voltage regulator regulates the supply voltage such that it becomes relatively insensitive to external power variations.
Beside a general demand for higher computational capabilities, low-power operation has become equally, if not more, important in recent years. Techniques, such as power gating, have become available for temporarily turning off selective circuit blocks that are not used in order to reduce overall leakage power of the chip. Such temporary shutdown time is called, for example, in the prior art “low power mode” or “inactive mode”. When the circuit blocks are required again for operation, they are activated to “active mode”. For maximizing power performance while minimizing impact to performance, these two modes are switched at an appropriate time and in a suitable manner.
Basically, prior art teaches two different regulator topologies for switching the voltage of a chip. Linear regulators operate using e.g. a transistor acting as a pass resistor in order to establish a fixed voltage at the output. Switching regulators are often mixed-mode circuits that feed back an analogue error signal and digitally gate it to provide bursts of current at the output.
However, linear regulators possess poor efficiencies in some operating modes, e.g. when the output voltages is much lower than the input voltage. Switching regulators exhibit some serious concerns when it comes to on-chip implementation, as they often require a large size of inductors and capacitors. Other drawbacks of voltage regulators known from prior art are, e.g., bald voltage stability when the current draw changes, suboptimum temperature stability and no compensation for silicon aging.